1. Technical Field
The invention relates to a method for manufacturing a pixel structure. Particularly, the invention relates to a method for manufacturing a pixel structure capable of reducing a number of masks.
2. Related Art
Liquid crystal displays (LCDs) have advantages of high image quality, small size, light weight, low driving power, low power consumption and wide application range, etc., which have replaced a cathode ray tube to become a mainstream of new generation displays. A conventional liquid crystal panel is composed of a color filter substrate, a thin film transistor array substrate and a liquid crystal layer disposed between the above two substrates. In order to improve display quality of the liquid crystal panel, many layout designs of a pixel structure in the display panel have been provided.
Generally, the thin film transistors are divided into amorphous silicon transistors and low temperature polycrystalline transistors according to channel layer materials thereof. However, to cop with increasing demands for the LCDs in the market, more efforts are put on research and development of new thin film transistor techniques. Among them, a thin film transistor using metal oxide as a channel layer has been developed, where an electrical characteristic thereof has caught up with the low temperature polycrystalline transistor, and the thin film transistor has a better effect in device performance.
Since the metal oxide is liable to be damaged by substances such as plasma, an etching liquid and a photoresist stripping liquid, etc. to change a thin film property of the channel layer. Thus, a thin film transistor pixel structure using the metal oxide such as indium gallium zinc oxide as the channel layer generally includes an etching stop layer disposed on the channel layer, six photomask processes are required in a manufacturing process. The six photomask processes include a first photomask process of forming a scan line and a gate, a second photomask process of forming a channel layer, a third photomask process of forming the etching stop layer, a fourth photomask process of forming a data line, a source and a drain, a fifth photomask process of forming a contact opening above the drain, and a sixth photomask process of forming a pixel electrode. However, the sixth photomask processes lead to high cost of the thin film transistor pixel structure, so that it is required to decrease the number of the photomasks required in a manufacturing process of the thin film transistor.